Nipple



FIG. 1 is a front elevational view of a nipple showing our new design;

FIG. 2 is a rear elevational view;

FIG. 3 is a side elevational view;

FIG. 4 is a top plan view; and

FIG. 5 is a bottom plan view.

The broken line showing of the bottle is for illustrative purposes only and forms no part of the claimed design. 

The ornamental design for a nipple, as shown and described. 